Synthesis, Characterization, and NLO Properties of a Phenothiazine−Stilbazole Monolayer

Abstract

4-( trans -4-(4-(10-phenothiazinyl)butyramido)styryl)pyridine (PBSP) has been synthesized and covalently bound to a coupling layer of ( p -(chloromethyl)phenyl)trichlorosilane (CPTS) on a quartz substrate to produce a polar-ordered thin film. The addition of the PBSP molecules on the coupling layer was monitored by FTIR spectroscopy, UV−visible spectroscopy, AFM, and second harmonic generation (SHG). The observation of an amine band and strong methylene bands in the infrared spectra indicates the presence of the PBSP layer. The UV−visible spectrum shows a red shift in the charge-transfer band, consistent with the addition of the PBSP and quaternization of the pyridyl group. AFM shows that there is an incomplete coverage of the PBSP layer on the coupling layer. The nonlinear optical properties of the PBSP monolayers were measured by SHG. The second harmonic (SH) signal increased by 1 order of magnitude after the addition of the PBSP chromophore layer. The dependence of the SH intensity on incident angle and input polarization was modeled. The average molecular orientation angle of the choromophore was determined to be 55°, and a value of χ zzz = χ zxx = 2.8 × 10 - 8 esu was calculated.